The invention relates to marine drive lower gearcases with a vertical driveshaft having a lower pinion gear driving a driven gear at the front of a torpedo housing. The driven gear drives a horizontal propeller shaft extending rearwardly out of the torpedo housing. The torpedo housing has a rearwardly opening bore which is threaded at the rear, and which has a front reduced diameter portion for receiving and retaining the driven gear which is press-fit forwardly into such front portion of the bore. The invention more particularly relates to a method and tool for installing the driven gear in the bore in the torpedo housing, and press-fitting the driven gear into the front portion of the bore without impacting same with hammer blows or the like.
In the lower gearcase of a marine drive, it is typical that the forward gear is at the front of the gearcase and supported by tapered roller bearings to bear forward axial thrust, for example U.S. Pat. Nos. 4,530,667, 4,792,313, incorporated herein by reference. Such gears are typically installed into the torpedo housing bore by inserting same forwardly and then inserting an axial shaft into the gear, which shaft has a shoulder engaging the gear, and then impacting the shaft with hammer blows or the like, to push the gear axially forwardly to press-fit same in a reduced diameter front portion of the torpedo housing bore. The tapered roller bearings are assembled to the gear prior to insertion into the torpedo housing, and the design of such tapered roller bearings to absorb forward axial propeller thrust also enables such bearings to absorb the noted hammer blow impact during installation.
In some marine applications, for example those known as lefthand shiftable, particularly involving dual drives, the front gear in the lower gearcase is the reverse gear, and the rear gear is the forward gear. In this implementation, the front gear need only absorb axial thrust while the drive is in reverse, which is only a small percentage of the time and which involves much lighter axial thrust loads than forward. Accordingly, the front reverse gear need not be supported by tapered roller bearings or other axial thrust bearings, but instead can be supported by ball bearings or the like. In this latter implementation, however, it is desirable not to install such front reverse gear by the above noted impact hammer blow technique because the inner and outer races of the ball bearing may slide axially relative to one another or otherwise dislodge or unseat the balls.
The present invention addresses and solves the noted problem in a particularly simple and efficient manner, without the need of previously used hammer blow impacting.